The principal aim of the proposed research is to develop an understanding of the mechanism of thrombogenesis at the surfaces of cardiovascular implants in contact with human blood. The adsorption and possible biochemical alterations of blood proteins on surfaces such as low-temperature isotropic pyrolytic carbon, used in heart valve prostheses, has been suggested as a necessary precurser to initiation or retardation of thrombus formation on all foreign surfaces. A unique procedure has recently been developed which enables the measurement of infrared spectra of adsorbed molecules on solid surfaces, with the infrared energy originating from "inside" the solid. This involves the use of thin films of carbon or other materials on an optically transparent internal reflection element, and subsequent adsorption from solution onto the exposed surface of the film. Infrared internal reflection spectra of the solid/protein interface will provide additional information on the types of interactions taking place at the surfaces of artificial implants when exposed to blood. This in turn should lead to an improved understanding of how the thrombogenic or thromboresistant nature of the surface is "transmitted" through the protein layer into the blood. This technique of measuring spectra of adsorbed species has obvious ramifications in other applications, such as catalysis and electrode surface reactions. The results of the proposed research will naturally form the basis for the expansion of research into these diverse areas.